Voice communication systems, including telephone systems, are subject to several sources of echo that make transmitted voice signals distorted, and thus unacceptable to listeners. Echoes can noticeably degrade the intelligibility and quality of a transmitted voice signal. Echoes associated with acoustic reverberation are particularly evident in connection with use of speakerphones. It is most often the case that users speaking into a speakerphone within small enclosed environments, such as offices or conference rooms, are unaware of the presence of such echoes.
One source of echo is simple acoustic reverberation generated at the user's physical location. For example, if the user employs a speakerphone, the user's voice may reflect off the surrounding environmental structure, such as the walls and ceiling. The reflected sound waves result in a plurality of random acoustic paths that are received by the microphone of the speakerphone. These random and time separated acoustic paths create echoes.
Another source of echo is acoustic feedback that may be created by use of a speakerphone by a remote party. Acoustic feedback originates as a voice signal generated by the user and transmitted to a remote party's location. The received voice signal is broadcast by the speaker in the remote party's speakerphone, the broadcasted voice signal reflects off the enclosed area and is picked up by the microphone of the speakerphone. The reflected voice signal is then transmitted back to the user as acoustic feedback.
Other echoes within a telecommunication system may result from hybrid unbalanced conditions within the particular communication hardware used in the communication system. More specifically for hybrid echoes, these often result from mismatches of impedances on PSTN networks.
Whether an echo is perceptible to a user is generally determined by the signal level of the echo, and the time offset or delay of the echo relative to the time in which the original signal is generated. The problem of echoes in voice communications is further aggravated by the use of packet data networks because packet data networks cause an increase in transmission delay times thereby making echoes more easily perceptible to users.
Attempts have been made to reduce echo in voice communications by the use of signal processing techniques to compensate for or remove the echoes. Generally, such techniques require the deployment of an echo canceller, a device combining hardware and firmware to achieve the signal processing. Such echo cancellers typically run on a digital signal processor that are programmed to sense echoes in voice signals and then to alter the voice signals to compensate for the presence of echoes.
With the advent of new telephony transmission protocols, echoes with increased or longer delays now reside over many communication networks. Cancellation of echoes is achieved in some echo cancellers by providing an estimate of the bulk echo delay that includes measurement by the echo canceller of the length of time of a particular echo delay as well as the magnitude of the echo. A number of telephony devices may include echo cancellation capability to include voice over IP phones, voice over IP media gateways, and PSTN gateways.
For telephone communications, there may be a need for confidentiality where one or both of the parties to a conversation may only wish for their conversation to be heard by the other party. For these types of confidential communications, it is undesirable to use a speakerphone since the relatively powerful speaker of the speakerphone may allow other parties to hear the conversation. Depending upon the particular location where and how a speakerphone is employed, a user may not know whether the remote party is using a speakerphone. Some acoustic echo is perceptible by a user, but not all. Thus, the user has no reliable way of knowing whether the remote party is using a speakerphone particularly when the user can perceive no echo. Even if the user requests the remote party to not use a speakerphone, the user has no reliable way of confirming whether the remote party has complied with the request.
Therefore, there is a need for providing an indication to a user of a telecommunication device as to the use of a speakerphone by a remote party. While echo detection and remediation is known in the use of echo cancellers, these echo cancellers do not provide a signal to the user indicating the presence of an echo, much less discriminating hybrid echo from acoustic echo for purposes of providing the signal to the user indicating the presence of a speakerphone.